Authenticated Relaying using Postfix

I'm having trouble configuring postfix to allow authenticated relaying of messages. I'm getting dizzy reading all of the how-tos around this topic and I'm not making sense of them.

I originally set up my box using a modified perfect server set-up for suse 10.2. I use postfixadmin to administer my email server. I'd like to be able to use the same mysql database to authenticate remote users. I know it can be done, but I can't figure out how to do it on my system.

You can check out the tutorials about "Virtual Users and Domains with Postfix ..." in the Postfix category: http://www.howtoforge.com/howtos/email/postfix
That should give you the idea. Unfortunately we have no such tutorial for SUSE.

I am still confused about logging in to postfix using a full email address. I would like to login to my account using Outlook and use my full email address a the username. Does the mysql virtual user setup solve this issue and does the database get updated by ispconfig. Ispconfig uses virtusertable to solve this issue with squirlmail and webmail. Is there a way to do the same with Outlook and other programs without setting up a complicated database. I was looking for something easy like adding:
virual_alias_maps = /etc/postfix/virtusertable
to main.cf, but this does not work. Can someone tell me why?